1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a transflective liquid crystal display device and method of fabricating a transflective liquid crystal display device.
2. Discussion of the Related Art
In general, display devices require low power consumption, high picture quality, thin profile, and light weight. Presently, liquid crystal display (LCD) devices are replacing conventional cathode ray tubes (CRTs).
In common liquid crystal display devices, an image is displayed by light radiated from a light source, i.e., a back-light device located on a lower part of a liquid crystal display panel. However, the amount of light actually transmitting through the liquid crystal display panel is about 7% of the light generated from the back-light device. Accordingly, a significant amount of the light produced by the back-light device is absorbed or blocked by the liquid crystal display panel. Thus, power consumption of the back-light is increased.
In order to solve the power consumption problem of the back-light device, reflective liquid crystal display devices that do not use the back-light device are being developed. These reflective liquid crystal display devices use natural light, thereby reducing power consumption of the back-light device, and thus allow portable use of the liquid crystal display devices. The reflective liquid crystal display devices make use of ambient light by reflecting the ambient light using an opaque material having reflective property within pixel areas of the liquid crystal display devices.
However, the ambient light is not always available. Accordingly, the reflective liquid crystal display devices can only be effectively used where an abundance of ambient light is available, and cannot be used in low light or dark environments. Thus, transflective liquid crystal display devices, which combine advantages of the reflective liquid crystal display devices using the natural light and of the transmission liquid crystal display devices using the back-light device, are being developed. The transflective liquid crystal display devices can be easily converted into reflection mode and transmission mode device by user selection.
In general, the transflective liquid crystal display devices simultaneously function like both the transmission mode liquid crystal display devices and the reflective mode liquid crystal display devices. Accordingly, the user may be able to use the light of the back-light device and the ambient light. Thus, operation of the transflective liquid crystal display devices is dictated or limited by environmental conditions, and the power consumption can be reduced.
FIG. 1 is a perspective view of a transflective liquid crystal display device according to the related art. In FIG. 1, a transflective liquid crystal display device comprises a color filter substrate 10 having a transparent common electrode 8 formed on a black matrix 6 and a color filter 7, a pixel area P having a pixel electrode 18 divided into a transmission part 16 and a reflection part 17, and an array substrate 20 having a switching device S and gate and data lines 13 and 14. In addition, a liquid crystal material layer 30 is formed between the color filter substrate 10 and the array substrate 20.
FIG. 2 is a partial cross sectional view of a transflective liquid crystal display device according to the related art. In FIG. 2, the array substrate 20 and the color filter substrate 10 having the switching device S and the color filter 7 on two transparent substrates 5 and 15 are disposed to face each other, respectively. In addition, the liquid crystal material layer 30 is formed between the array substrate 20 and the color filter substrate 10.
The switching device S is formed on the array substrate 20 and is disposed in a pixel region for supplying and blocking a signal voltage to the liquid crystal material layer 30. The switching device S includes a gate electrode 21 to which a scan signal is supplied, an active layer 23 having a semiconductor layer 23a activated in response to the scan signal to form a channel, and an n+ doped ohmic contact layer 23b that is formed on both sides of the semiconductor layer 23a, a gate insulating layer 24 for electrically insulating the active layer 23 from the gate electrode 21, a source electrode 24 formed on the active layer 23 to which a data signal is input, and a drain electrode 25 transmitting the data signal input to the source electrode 24 to the pixel electrode when the semiconductor layer 23a is activated. In addition, a passivation layer 26 is formed on an entire surface of the array substrate 20 for protecting the source electrode 24 and the drain electrode 25. Moreover, a contact hole 29 is formed on the passivation layer 26 to electrically connect the drain electrode 25 to the pixel electrode 27.
The black-matrix 6 is formed within an area of the color filter substrate 10 corresponding to the area where the switching device S is formed in order to block the light and prevent it from being transmitted into areas above the black matrix 6. In addition, the pixel electrode 27, which is connected to the drain electrode 25 through the contact hole 29, is formed on the pixel region P (in FIG. 1) except at the portion where the switching device S is formed, and a reflective electrode 28 made of a metal having high reflection properties is formed on the pixel electrode 27.
A portion of the reflective electrode 28 is removed to form a transmitting portion 16 having a width t. As described above, the transmission part 16 is formed within the pixel region P, whereby the light input from a direction of the transparent substrate 5 is reflected by the reflection electrode 28 and emitted along the same direction of the transparent substrate 5 in the reflection mode. In addition, the light emitted from the back-light device adjacent to the transparent substrate 15 is transmitted through the transmission part 16 in the transmission mode to produce an image.
A concave recess portion is formed within the area where the transmission part 16 is formed by removing portions of the passivation layer 26 and the reflection electrode 28. The transmission part 16 is formed to have a concave recess shape in order to match ON/OFF modes of the reflection part and the transmission part 16 and to maximize the efficiency of the transmission mode. In addition, it is desirable that a ratio between a cell gap d2 of the transmission part 16 and a cell gap d1 of the reflection part is to be 2:1, that is, d2 is to be twice d1. Accordingly, the transmission efficiencies on the reflection part and on the transmission part 16 are theoretically the same.
However, in the transflective liquid crystal display device according to the related art, the switching device S formed on the array substrate 20 is adversely affected by the process of etching the passivation layer 26 on the array substrate 20. Accordingly, inferiority of the switching device S may be generated. For example, the switching device S, the gate insulating layer 22, the passivation layer 26, and the transparent electrode 27 formed on the array substrate 20 are affected by the process of forming the step in the passivation layer 26.